The safety, cost and suitability of nuclear energy is to be assessed by the Health and Safety Executive, the BBC has learnt.
The government is asking industry and the public for ideas
Ministers have asked the HSE to look at existing nuclear plants, it has emerged on the day a public consultation on the energy issue is being launched.
Environmental campaigners fear the HSE study is a prelude to an expansion of Britain's nuclear network.
But the government insisted no decision had been taken on nuclear.
The HSE will also look into the viability of other ways to generate power; such as wind turbines, gas transport and storage, and carbon capture and storage.
The government launched an energy review in November, and the public consultation period is starting on Monday.
There is concern over the reliability of Britain's energy sources, especially after recent gas price rises.
It is thought the HSE review - set to take 18 months - has been requested to save time if the government does give the go-ahead for new power stations.
It would enable the nuclear industry to begin work more quickly.
BBC science correspondent Pallab Ghosh said the government was likely to say the review was not the "pre-licensing" of reactors that the nuclear industry has been pressing for.
He said green groups believed the government had already made its mind up on the issue and would see this is a "major step" toward pre-licensing.
"It's a process [green groups] see as paving the way for new power stations rather than one that makes sensible preparations," he explained.
Trade and Industry Secretary Alan Johnson is launching the three-month public consultation on Monday, seeking opinions from industry, environmentalists and the public.
Business leaders said British firms would be less competitive if energy became more expensive or unreliable.
But environmental campaigners have said there is no need to build new nuclear power stations when there are greener alternatives.
Tony Juniper, executive director of Friends of the Earth, said energy policy was "at a crossroads".
"We can tackle climate change and meet our energy needs by cutting waste, harnessing the power of renewables and using fossil fuels more efficiently," he said.
But the Engineering Employers Federation, which represents thousands of companies, said the government had to quickly decide on a coherent energy plan and had to consider all options, including nuclear power.
Director general Martin Temple said: "Energy is now right at the top of the agenda and there is no time to lose in putting in place a long-term strategy that will provide a competitive, reliable and secure supply and generate significant reduction in emissions."
The Energy Saving Trust said there was a pressing need to solve "escalating demand for energy" while still keeping the UK's carbon-emission quotas to Kyoto Protocol targets.